System and method for strengthening tubular and round tower members

ABSTRACT

A system and method for strengthening elongated members of a tower section is provided. A tower section includes a plurality of elongated members. At least one reinforcing member is employed to reinforce the tower section. A structural adhesive is applied to the elongated members and the reinforcing members. The reinforcing members are pressed or otherwise placed against corresponding elongated members. The structural adhesive is cured to thereby permanently attach the reinforcing members to the corresponding elongated members. The reinforcing members can be clamped, bolted or otherwise secured to the corresponding elongated members during curing of the structural adhesive.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. ProvisionalApplication Serial No. 60/415,906 filed on Oct. 3, 2002 entitled “AMethod for Strengthening Tubular and Round Tower Members”, thedisclosure of which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

[0002] This invention relates generally to structural reinforcementsystems, and more particularly relates to a system and method forstrengthening tubular and round tower members.

BACKGROUND OF THE INVENTION

[0003] Existing systems and methods of reinforcing steel tubes or solidrounds of tower members require bolting or welding of heavy steelreinforcements which are difficult to position and install. Welding andbolting in the field is costly in both labor and time. When existingsteel is galvanized, welding can often damage the galvanizing atlocations that are not practical to repair later. Moreover, there is therisk that welding sparks dropping onto areas away from the tower cancause damage to property. When only bolting is used, high clampingforces are necessary to provide friction between the existing member andthe new reinforcing member to transfer the shear forces between them.These clamping forces are questionable in their ability to be effectivein reducing buckling behavior. Further, the application of weld joints,bolts or permanent clamps to a tower can significantly aestheticallydetract from the appearance of the tower.

[0004] Accordingly, it is a general object of the present invention toovercome the above-identified drawbacks of prior systems and methods forstrengthening towers.

SUMMARY OF THE INVENTION

[0005] The present invention resides in a system and method forstrengthening elongated members of a tower section. A tower sectionincludes a plurality of elongated members. At least one reinforcingmember is employed to reinforce the tower section. A structural adhesiveis applied to the elongated members and the reinforcing members. Thereinforcing members are pressed or otherwise placed againstcorresponding elongated members. The structural adhesive is cured tothereby permanently attach the reinforcing members to the correspondingelongated members. The reinforcing members can be clamped, bolted orotherwise secured to the corresponding elongated members during curingof the structural adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 is a side elevational view of a tower section withreinforcing members in accordance with the present invention.

[0007]FIG. 2 is a top plan view of a reinforcing member secured to ahollow pipe of a tower section and temporarily held in place by bolts.

[0008]FIG. 3 is a top plan view of a reinforcing member secured to asolid round member of a tower section and temporarily held in place bybolts.

[0009]FIG. 4 is a top plan view of an outside reinforcing member securedto a member of a tower section and temporarily held in place by a U-boltclamp.

[0010]FIG. 5 is a top plan view of outside and inside reinforcingsections secured to a member of a tower section and temporarily held inplace by a full circle clamping device.

[0011]FIG. 6 is a top plan view of a reinforcing member in the form of aclamp secured to a member of a tower section.

[0012]FIG. 7 is a top plan view of a reinforcing member includingoverlapping parts secured to a member of a tower section.

[0013]FIG. 8 is a top plan view of an outside reinforcing member securedto a member of a tower section with spacers interposed between thereinforcing member and the member of the tower section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] With reference to FIG. 1, a tower section that is reinforced inaccordance with the present invention is indicated generally by thereference number 10. The reinforcement may be used for increasing theaxial load carrying capacity of the legs of the tower section orincreasing the buckling capacity by making the section more compact. Thetower section includes a plurality of vertically extending elongatedmembers or legs 12 which can be either hollow or solid in cross section.The elongated members 12 are preferably made of a metal such as steel,but may be fabricated from other relatively strong and durable materialswithout departing from the scope of the present invention.

[0015] The tower section 10 can include leg splices 14 for couplingadjacent tower sections to one another. The elongated members 12 arecoupled to one another by lateral supports or cross bracing membersincluding horizontal members 16 and diagonal members 18 fabricated fromthe same or similar materials as the elongated members.

[0016] Reinforcing members indicated generally by the reference number20 are coupled to the elongated members 12, as explained more fullybelow, for increasing structural integrity to the tower section 10. Alength of the reinforcing members 20 can vary, but is preferably nearlyabout a distance between lateral support connections along the elongatedmember 12 being reinforced. The reinforcing members 20 are preferablyfabricated from metallic materials such as steel, or fiber reinforcedpolymer (FRP) materials such as carbon fibers encapsulated in a resinmatrix. However, the reinforcing members 20 can be fabricated from otherstrong, durable and adherable materials without departing from the scopeof the present invention.

[0017] As shown in FIG. 1, each of the reinforcing members 20 isgenerally in the form of two half pipe sleeves which cooperate to form acircle in cross section and thereby extend substantially about theperimeter of a corresponding elongated member 12. More specifically, afirst semi-cylindrical or half pipe sleeve serves as an outwardly facingor outside reinforcing section 20 a, and a second semi-cylindrical orhalf pipe sleeve can optionally serve as an inwardly facing or insidereinforcing section 20 b. A cross-sectional diameter of the reinforcingmember 20 can vary depending on the diameter of the elongated member 12that is being reinforced. Moreover, the reinforcing members 20 cantypically extend about 90 degrees to about 360 degrees around theperimeter of the corresponding elongated member 12 being reinforcedwithout departing from the scope of the present invention.

[0018] As shown in FIG. 1, the inside reinforcing sections 20 b arediscontinuous along portions 21 of the elongated member 12 that arecoupled to cross bracing members 16, 18. The reinforcing members 20 areadhered to the elongated members 12 with a structural adhesive.Moreover, the reinforcing members 20 can optionally be adhered to thecross bracing members including either or both of the horizontal members16 and the diagonal members 18. Clamps or thru-bolts indicated by thereference number 22 are temporarily or permanently applied to thereinforcing members 20 in order to hold the reinforcing members to theelongated members of the tower section 10 during adhesive curing. Asexplained more fully below, the reinforcing members 20 can be designedto self-clamp to an elongated member 12.

[0019] Although the elongated members 12 of the tower section 10 and thereinforcing members 20 are shown as circular or semi-circular incross-section, the members can take other practical shapes or sectionsof shapes such as, for example, rectangles or squares without departingfrom the scope of the present invention.

[0020] In operation, the reinforcing members 20 are adhered to the towersection 10 using conventional structural adhesives. The reinforcingmembers 20 are held in place during installation using bolts, clampingdevices or other means that include overlapping portions of thereinforcing member. As shown in FIG. 2, for example, an elongated memberin the form of a hollow pipe 12 a has gussets 24 extending therefrom,and is reinforced by a reinforcing member 20 in the form of two halfpipe sleeves. The half pipe sleeves serve as an outside reinforcingsection 20 a and an optional inside reinforcing section 20 b whichcooperate to extend substantially about the perimeter of the elongatedmember 12. The reinforcing member 20 can define notches 26 for receivingoptional step bolts 28 to hold the reinforcing member in place duringadhesive curing. As shown in FIG. 3, the elongated member beingreinforced can be in the form of a solid round member 12 b.

[0021] A reinforcing member 20, such as the outside reinforcing section20 a in the form of a half pipe sleeve shown in FIG. 4, can be securedto the elongated member 12 with a U-bolt clamp 30 or other clampingdevice. As further examples of clamping devices, FIG. 5 shows areinforcing member 20 in the form of two half pipe sleeves 20 a, 20 bbeing held in place to the elongated member 12 with a clamping device 32which extends substantially around a perimeter of the reinforcingmember.

[0022] The reinforcing member itself may serve as a clamp. As shown inFIG. 6, for example, the reinforcing member 20 includes two reinforcingsections each in the form of half pipe sleeves 20 c. Each half pipesleeve 20 c defines two opposing flanges 34 for being abutted to acorresponding flange of the other half pipe sleeve. The abutting flanges34 are secured to one another by bolts 36.

[0023] Alternatively, as shown in FIG. 7, the reinforcing member 20 caninclude first and second reinforcing sections 20 d, 20 e each generallyin the form of half pipe sleeves. The first reinforcing section 20 dfurther defines two opposing overlap portions 38 each of which can bepress fitted or otherwise secured over an adjacent portion of the secondreinforcing section 20 e to thereby self-clamp the reinforcing member 20to the elongated member 12.

[0024] When FRP materials are used as a reinforcing member, the clampingdevice used is located on the outside of the reinforcing member to applypressure onto the adhesive until it is cured. This allows the contractorinstalling the FRP pipe member to ensure that the adhesive is properlypressed against the existing member and the bond line thickness of theadhesive between the existing tower member and reinforcing member iscorrect. To provide additional accuracy in ensuring an accurate bondline thickness, a spacer made of plastic, string or metal can be placedbehind the reinforcing member prior to tightening the clamping device.As shown in FIG. 8, for example, spacers 40 are interposed between areinforcing member 20 in the form of a half pipe sleeve and theelongated member 12.

[0025] When metal is used as the reinforcing member on existing circularmembers in the vertical position (e.g. tower legs), the reinforcementmay require a vertical support while the adhesive is curing.

[0026] The structural adhesive is placed between the surface of thereinforcing member and the tower structure. The adhesive is placed ontothe reinforcing member itself prior to placing onto the tower ordirectly onto the existing steel member prior to pressing thereinforcing member into it. The adhesive is the primary means oftransferring loads between the reinforcing member and the towerstructure. The loads are transferred in shear.

[0027] The locations and requirements of the reinforcements areidentified in the structural design. The reinforcements are cut to theircorrect lengths prior to delivery to the site or field cut. When thereinforcing member is made of an FRP material, the inside surface of themember is sanded or surface prepared in the molding to ensure a goodbond transfer between the FRP and adhesive. When the reinforcing memberis steel and hot dip galvanized, a surface preparation of the side toreceive the adhesive may be required. Depending on the quality of thegalvanizing and its bond to the steel, this surface preparation mayentail cleaning and etching (chemical or abrasive) or removing thegalvanizing layer altogether. When available, a primer may be applied tothe bare steel after it has been exposed to reduce the amount ofoxidation that will begin to occur.

[0028] With the reinforcing members on site, the existing tower membersto be reinforced are prepared for the adhesive by sanding, sandblastingor a chemical wash. Adhesive is next placed onto the surface and aspacer material can be placed on the adhesive. In lieu of spacermaterials placed on the adhesive in the field, glass beads having theproper diameter may be mixed in with the adhesive at the time of mixingthe adhesive components. The reinforcing members are then lifted intoposition and pressed onto the tower legs using a clamping device. Onceinstalled, clamps or bolts can be placed and used to position and pressthe reinforcing members. The need to leave the clamping device in placeis optional and depends on the design and construction methods used.

[0029] The present invention utilizes structural adhesives to transferthe shear forces between the existing member and the new reinforcingmember, eliminating the requirement for permanent welding or clamping.The elimination of welding and friction clamping in the field providescost savings in labor and time. Eliminating field welding removes therisk of welding sparks dropping onto areas away from the tower andcausing damage to property. It also eliminates welding damage to thegalvanizing layer that exists on the inside of a tubular member whenwelded to the outside of the member. The latter is particularlyimportant as inspection on the inside of a tubular member is impracticalto accomplish.

[0030] The completed retrofit reinforcement is low profile—meaning thatno major projections exist from the tower when the retrofit work iscomplete. In addition to the aerodynamic advantages, this has benefitsto tower owners and local communities who have aesthetic concerns aboutthe appearance of their towers.

[0031] As will be recognized by those of ordinary skill in the pertinentart, numerous modifications and substitutions may be made to theabove-described embodiment of the present invention without departingfrom the scope of the invention. Accordingly, the preceding portion ofthis specification is to be taken in an illustrative, as opposed to alimiting sense.

What is claimed is:
 1. A method of strengthening elongated members of atower section, comprising the steps of: providing a tower sectionincluding a plurality of elongated members; providing at least onereinforcing member; applying structural adhesive to at least one of theplurality of elongated members and the at least one reinforcing member;placing the at least one reinforcing member against a corresponding oneof the plurality of elongated members; and curing the structuraladhesive to thereby permanently attach the at least one reinforcingmember to the corresponding one of the plurality of elongated members.2. A method as defined in claim 1, wherein the plurality of elongatedmembers include vertically extending members.
 3. A method as defined inclaim 2, wherein the plurality of elongated members further includecross bracing members coupling the vertically extending members to eachother.
 4. A method as defined in claim 1, wherein the step of applyingincludes placing the structural adhesive onto the at least onereinforcing member.
 5. A method as defined in claim 1, wherein the stepof applying includes placing the structural adhesive onto the at leastone of the plurality of elongated members.
 6. A method as defined inclaim 1, further including the step of introducing a spacer interposedbetween the at least one of the plurality of elongated members and theat least one reinforcing member prior to the step of placing.
 7. Amethod as defined in claim 6, wherein the step of introducing a spacerincludes mixing glass beads into the structural adhesive.
 8. A method asdefined in claim 6, wherein the spacer is composed of a materialincluding one of plastic, string, and metal.
 9. A method as defined inclaim 1, further including the step of clamping the at least onereinforcing member to that at least one of the plurality of elongatedmembers during the step of curing.
 10. A method as defined in claim 9,further including the step of terminating the step of clamping after thestep of curing is complete.
 11. A method as defined in claim 1, furtherincluding the step of preparing the at least one of the plurality ofelongated members for receiving the structural adhesive by one ofsanding, sandblasting, and a chemical wash.
 12. A method as defined inclaim 1, further including the step of preparing the at least onereinforcing member for receiving the structural adhesive should the atleast one reinforcing member have a galvanizing layer.
 13. A method asdefined in claim 12, wherein the step of preparing the at least onereinforcing member includes one of cleaning, etching, and removing thegalvanizing layer.
 14. A method as defined in claim 13, wherein thecleaning, etching, or removing is accomplished by one of chemical andabrasive means.
 15. A method as defined in claim 13, wherein the step ofpreparing the at least one reinforcement member further includesapplying a primer.
 16. A tower section reinforcement system comprising:a tower section including a plurality of elongated members; and at leastone reinforcing member coupled to the at least one of the plurality ofelongated members by structural adhesive.
 17. A tower sectionreinforcement system as defined in claim 16, wherein the elongatedmembers include vertically extending members.
 18. A tower sectionreinforcement system as defined in claim 17, wherein the elongatedmembers further include cross bracing members coupling the verticallyextending members to each other.
 19. A tower section reinforcementsystem as defined in claim 16, wherein the plurality of elongatedmembers are each generally circular in cross-section.
 20. A towersection reinforcement system as defined in claim 19, wherein the atleast one reinforcing member is generally circular in cross section. 21.A tower section reinforcement system as defined in claim 20, wherein theat least one reinforcing member includes an outwardly facing reinforcingsection extending partially about a perimeter of a correspondingelongated member.
 22. A tower section reinforcement system as defined inclaim 21, wherein the at least one reinforcing member further includesan inwardly facing reinforcing section extending partially about theperimeter at a location generally opposite to that of the outwardlyfacing reinforcing section.
 23. A tower section reinforcement system asdefined in claim 22, wherein the outwardly facing reinforcing sectionand the inwardly facing reinforcing section cooperate to extend about 90degrees to about 360 degrees around the perimeter.
 24. A tower sectionreinforcement system as defined in claim 22, wherein the outwardlyfacing reinforcing section and the inwardly facing reinforcing sectioneach include flanges at opposing ends, each of the flanges of one of thereinforcing sections being abutted and coupled to a corresponding flangeof the other reinforcing section, whereby the outwardly facingreinforcing section and the inwardly facing reinforcing sectioncooperate to form a clamp.
 25. A tower section reinforcement system asdefined in claim 22, wherein one of the outwardly facing reinforcingsection and the inwardly facing reinforcing section includes overlapportions at opposing ends, each of the overlap portions being securedover an adjacent portion of the other reinforcing section, whereby theoutwardly facing reinforcing section and the inwardly facing reinforcingsection cooperate to form a clamp.
 26. A tower section reinforcementsystem as defined in claim 16, further including at least one clamp forsecuring the at least one reinforcing member to an associated elongatedmember during curing of the structural adhesive.
 27. A tower sectionreinforcement system as defined in claim 26, wherein the at least oneclamp is a U-bolt clamp.
 28. A tower section reinforcement system asdefined in claim 26, wherein the at least one clamp extendssubstantially around a perimeter of the associated elongated member. 29.A tower section reinforcement system as defined in claim 22, wherein theoutwardly facing reinforcing section and the inwardly facing reinforcingsection define notches for receiving bolts for securing the reinforcingsections to the associated elongated member during curing of thestructural adhesive.
 30. A tower section reinforcement system as definedin claim 16, further including a spacer interposed between the at leastone reinforcing member coupled to the at least one of the plurality ofelongated members.
 31. A tower section reinforcement system as definedin claim 30, wherein the spacer is made from one of plastic, string, andmetal.
 32. A tower section reinforcement system as defined in claim 30,wherein the spacer includes glass beads mixed with the structuraladhesive.
 33. A tower section reinforcement system as defined in claim16, wherein the plurality of elongated members are hollow in crosssection.
 34. A tower section reinforcement system as defined in claim16, wherein the plurality of elongated members are solid in crosssection.
 35. A tower section reinforcement system as defined in claim16, wherein the at least one reinforcing member is fabricated from amaterial including one of metal, and a fiber reinforced polymer.
 36. Atower section reinforcement system as defined in claim 35, wherein themetal includes steel.
 37. A tower section reinforcement system asdefined in claim 35, wherein the fiber reinforced polymer includescarbon fibers encapsulated in a resin matrix.
 38. A tower sectionreinforcement system as defined in claim 16, wherein the plurality ofelongated members are fabricated from a material including metal.
 39. Atower section reinforcement system as defined in claim 38, wherein themetal includes steel.